1. Field of the Invention
The present invention relates to a camera, and, more particularly, to a camera with a lens barrel unit provided in an outer case member, having a lens barrel unit layout and the structure of an outer case member, both of which are designed in consideration of reduction in shock loading and high impact resistance.
2. Description of the Related Art
It is desired that cameras or the like should be compact so that a user can easily carry a camera around, and take out and use it whenever desirable.
Accordingly, conventional cameras have a lens barrel unit whose casing is made flatter by using a bending optical system. Available bending optical systems include, for example, a system configured so as to bend the optical axis of a light beam input to an optical member from a front face side by using a reflector or the like to guide the light beam to the light receiving face of an image pickup device disposed at the bottom face or the like in the casing.
The conventional cameras with compact and flat casings realized with various measures taken, such as use of the bending optical system as a shooting optical system, have been made practical and become popular.
A user can easily carry around such a conventional camera with a compact and flat casing realized with the various measures taken, and use it whenever desirable. While the user is carrying around or using the camera, for example, the user is likely to drop the camera unintentionally or cause the camera to bump on some structure.
When external force originating from an unintentional shock or the like is applied to the casing of a camera while the camera is being carried around or is in use, an unnecessary load is applied to internal components of the camera, such as the lens barrel unit, as well as the outer case member which forms the casing of the camera.
In the casing of an ordinary camera, a plurality of optical lenses or the like are held in such a way that their optical axes coincide with one another. Further, components having movable parts, such as the lens barrel unit capable of moving some of the optical lenses in directions along the optical axes, are disposed in the casing.
In such a camera, for example, when external force in the direction in which the lens hold frame of the lens barrel unit moves, i.e., the same direction as the direction along the optical axis of an optical lens, is applied to the casing of the camera, the lens hold frame and the optical lens may be damaged.
FIG. 11 is a diagram of essential components (lens hold frames, etc.) of the lens barrel unit of a conventional camera extracted therefrom and viewed from the back face.
A lens barrel unit 121 shown in FIG. 11 has a bending optical system which bends an optical axis O1 of a light beam, input from the front face side, by means of a reflector 130a secured to a first lens hold frame 130 to guide the input light beam in a direction along an optical axis O2, i.e., toward the bottom face.
The essential portions of the lens barrel unit 121 include the first lens hold frame 130, a second lens hold frame 124, a third lens hold frame 125, a fourth lens hold frame 126, a slide shaft 122a and a slide shaft 122b. 
The first lens hold frame 130 holds a first group of lenses (not shown) disposed to face frontward, and the reflector 130a. The second lens hold frame 124 holds a second group of lenses 124a that is a movable lens group movable in a direction of an arrow M shown in FIG. 11 along the slide shafts 122a, 122b. The third lens hold frame 125 holds a third group of lenses 125a movable in the same direction M. The fourth lens hold frame 126 holds a fourth group of lenses 126a. The slide shaft 122a holds one ends of the first to fourth lens hold frames 130, 124, 125, 126 in such a way that the optical axes of the individual lens groups coincide with one another, and guides the movements of the second and third lens hold frames 124, 125. The slide shaft 122b holds the other ends of the third and fourth lens hold frames 125, 126, and guides the movement of the third lens hold frame 125.
Generally, the lens barrel unit 121 is arranged inside the camera in such a way that the optical axis O2 coincides with the vertical direction (direction of an arrow X in FIG. 11).
When the camera having the thus configured lens barrel unit 121 disposed inside the casing falls in, for example, the vertical direction (X direction), impact force is generated on, for example, the second lens hold frame 124 in a direction indicated by an arrow F0 in FIG. 11 (same direction as the vertical direction X).
When the fall-oriented impact force is applied to the individual components of the lens barrel unit 121, the lens hold frames, the lens groups, etc. may be damaged. Of those damageable components, particularly, the second lens hold frame 124 of the second group of lenses 124a which are movable lenses are cantilevered so as to be movably held only by the slide shaft 122a. Accordingly, bending moment in a direction of an arrow R in FIG. 11 (counterclockwise direction in FIG. 11) acts on the second lens hold frame 124 at the same instant as the camera falls.
In this respect, there have been various proposals made on a technique of relaxing, suppressing or absorbing the impact force to be applied to the internal components of a camera, particularly, the lens barrel unit, as much as possible when the camera falls or collides with something.
For example, a camera disclosed in Japanese Patent Application Laid-Open No. 2005-292514 has an urging member like a coil spring fitted over the slide shaft of the lens hold frame of a lens barrel unit. This configuration relaxes the shocks caused by the external force in the slide direction of the lens hold frame along the optical axis of an optical lens, and increases the contact area with which the lens hold frame contacts, thereby relaxing the intensive stress on the contact portion.
Another camera disclosed in, for example, Japanese Patent Application Laid-Open No. H5-333254 has a lens barrel unit whose lens frame is provided with a spring member which applies an urging force vertical to the optical axis, the guide shaft and the drive shaft, and with which the drive shaft is pressed engaged.